Determine if the Tono-Vera Tonometer accurately measures intraocular pressure (IOP). The hypothesis of this test is to confirm the Tono-Vera Tonometer is equivalent to the Goldmann Applanation Tonometer (within +/- 5.0 mmHg).

The Tono-Vera Tonometer (Reichert, Inc.) is a portable rebound tonometer intended to measure IOP. Subjects will undergo a standard ophthalmologic examination. Subjects will then be measured with four tonometers: Goldmann Applanation Tonometer (C.S.O. SRL), Ocular Response Analyzer G3 (Reichert, Inc.), iCare ic100 tonometer (iCare Finland Oy), and Tono-Vera Tonometer.

Inclusion Criteria:

• Subjects must be male or female, between the ages of 18 and 90 years old;
• Be able and willing to provide signed informed consent
• Be able to follow study instructions

Exclusion Criteria:

• Subjects with only one functional eye;
• Subjects with one eye having poor or eccentric fixation;
• Subjects with central corneal thickness greater than 600 µm or less than 500 µm (about 2 standard deviations the human mean);
• Subjects with corneal scarring or who have had corneal surgery, including corneal laser surgery;
• Subjects with concomitant ocular diseases such as: microphthalmos, buphthalmos, nystagmus, keratoconus, severe dry eye syndrome, blepharospasm, any other corneal or conjunctival pathology or infection;
• Contact lens wearers;
• Known allergy to proparacaine or fluorescein as these are used to anesthetize the eye and allow IOP measurement, respectively, when used with the GAT.